Since top of my list of things to do when riding is ‘staying alive’, closely followed by ‘not hurting myself’, I am a big believer in getting formal motorbike training. I’m not doing it every week but every so often (at least once a year) is a rule I live by. See below for the courses I have taken.
I have also completed:
California Superbikes School Level 2
California Superbikes School Level 3
and a couple of private lessons with HART
Not directly about riding skills, but very much related, I attended a First Aid For Motorcyclists course – this one is essential (IMHO) for anyone out and about, both near and far from civilisation.